scholarly journals Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Yang ◽  
An-yu Yang ◽  
Yan-gong Shan ◽  
Miao-miao Yang ◽  
Jin-lei Zhao ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Hysteresis Loop ◽  
Triaxial Test ◽  
Volumetric Strain ◽  
Rate Of Change ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Water Drainage ◽  
Cemented Sand ◽  
Sand And Gravel

Lean cemented sand and gravel (LCSG) materials are subjected to unloading-loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading-unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading-unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress-strain curves exhibiting a crescent-shaped hysteresis loop, which differs from that exhibited by coarse-grained soil. Although the shape of the crescent-like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent-like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

Experimental Study on Mechanical Characteristics of CSG Materials

2011 ◽  
Vol 243-249 ◽  
pp. 2059-2064
Author(s):  
De Gao Zou ◽  
Dong Qing Li ◽  
Bin Xu ◽  
Xian Jing Kong
Keyword(s):  
Mechanical Characteristics ◽  
Shear Failure ◽  
Triaxial Tests ◽  
Cemented Sand ◽  
Optimum Water Content ◽  
Strain Relationship ◽  
Mode Stress ◽  
New Type ◽  
Sand And Gravel ◽  
Optimum Water

Cemented sand and gravel (CSG) is a new type of dam materials. It not only can reduce the waste of resources and environmental pollution, but has the merits of both gravel and concrete. In this study, Cemented sand and gravel specimens with three cement ratios were compacted at optimum water content and cured for 14 days. Based on the consolidated drained shear triaxial tests, the mechanical properties of different proportion of CSG are studied on shear failure mode, stress-strain relationship, shear strength. Research results showed that, with the increasing of the content of cement, the peak and residual strength of CSG were improved, but the failure strains were decreased. In addition, CSG material behaves distinctly softening.

scholarly journals Large-Scale Triaxial Tests on Dilatancy Characteristics of Lean Cemented Sand and Gravel

2021 ◽  
Vol 9 ◽  
Author(s):  
Hang Yu ◽  
Xue-mei Shen ◽  
Yu-chen Ye ◽  
Jie Yang ◽  
Chen-hui Zhu
Keyword(s):  
Plastic Strain ◽  
Strain Increment ◽  
Triaxial Tests ◽  
Volume Strain ◽  
Triaxial Loading ◽  
Cemented Sand ◽  
Plastic Strain Increment ◽  
Loading And Unloading ◽  
Sand And Gravel ◽  
Increment Ratio

The dilatancy equation, which describes the plastic strain increment ratio and its dependence on the stress state, is an important component of the elastoplastic constitutive model of geotechnical materials. In order to reveal their differences of the dilatancy value determined by the total volume strain increment ratio and the real value of lean cemented sand and gravel (LCSG) materials, in this study, a series of triaxial compression tests, equiaxial loading and unloading tests, and triaxial loading and unloading tests are conducted under different cement contents and confining pressures. The results reveal that hysteretic loops appear in the stress–strain curves of equiaxial loading and unloading tests, and triaxial loading and unloading tests and that the elastic strain is an important component of the total strain. The hysteretic loop size increases with an increase in the stress level or consolidation stress, whereas the shape remains unchanged. Furthermore, with an increase in the cement content, the dilatancy value determined by the total volume strain increment ratio becomes smaller than that determined by the plastic strain increment ratio, and the influence of the elastic deformation cannot be ignored. Thus, in practical engineering scenarios, especially in the calculation of LCSG dam structures, the dilatancy equation of LCSG materials should be expressed by the plastic strain increment ratio, rather than the total volume strain increment rati.

scholarly journals Effect of Cement Content on the Deformation Properties of Cemented Sand and Gravel Material

2019 ◽  
Vol 9 (11) ◽  
pp. 2369 ◽  
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Xing-Wen Guo ◽  
Jin-Lei Zhao
Keyword(s):  
Cement Content ◽  
Axial Strain ◽  
Constitutive Models ◽  
Volumetric Strain ◽  
Prediction Method ◽  
Confining Pressure ◽  
Cemented Sand ◽  
Initial Modulus ◽  
Deformation Properties ◽  
Sand And Gravel

Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect of cement content on the deformation properties of CSG material, we employ triaxial compressive tests for cement contents of 20, 40, 60, 80, and 100 kg/m3 with a confining pressure range of 0.3–1.2 MPa, and theoretically analyze the results by the regression analysis prediction method. Here, we show that both cement content and confining pressure influence the deformation properties of CSG material: for an increase in cement content, the failure strain decreases and brittleness of CSG material increases; the initial modulus of the CSG material increased exponentially with increasing cement content or confining pressure; the peak volumetric strain and its corresponding axial strain increase linearly with increasing confining pressures, which decrease with increasing cement content; the initial tangent volumetric ratio can also be determined by the peak volumetric strain and its corresponding axial strain.

scholarly journals Small-Strain Dynamic Properties of Lean Cemented Sand and Gravel Materials under Different Cementing Agent Contents

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Yangong Shan ◽  
Miaomiao Yang ◽  
Xingwen Guo ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Small Strain ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Engineering Applications ◽  
Cemented Sand ◽  
Sand And Gravel ◽  
Cementing Agent

Lean cemented sand and gravel (LCSG) materials are increasingly being used in dams, embankments, and other civil engineering applications. Therefore, their mechanical properties and stress-strain behavior should be systematically understood. In this study, the small-strain dynamic properties of LCSG materials were examined. A series of dynamic triaxial tests were performed to investigate the effects of the confining pressure and cementing agent content of the material on its dynamic shear modulus (Gd) and damping ratio (λ). The results show that Gd increased and λ decreased with increasing confining pressure and cementing agent content; however, under the same confining pressure and cementing agent content, Gd decreased gradually in accordance with shear strain. Furthermore, new expressions were derived for Gd and λ, as well as for their maxima. The results of this study could provide a reference for practical engineering applications, including the construction of dams using LCSG materials.

scholarly journals Work input analysis for soils with double porosity and application to the hydromechanical modeling of unsaturated expansive clays

2017 ◽  
Vol 54 (2) ◽  
pp. 173-187 ◽  
Author(s):  
Jian Li ◽  
Zhen-Yu Yin ◽  
Yujun Cui ◽  
Pierre-Yves Hicher
Keyword(s):  
Mechanical Behavior ◽  
Expansive Soils ◽  
Volumetric Strain ◽  
Double Porosity ◽  
Strain Increment ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Expansive Clay ◽  
Expansive Clays ◽  
Boom Clay

A mechanical approach for unsaturated expansive soils considering double porosity has been developed based on the porous media theory. In this approach, the adsorbed and the capillary water, as well as the micropores and macropores, are two distinct phases. An interaggregate stress considered as the work-conjugate of the macrostructural strain increment has been defined. Both physicochemical and capillary effects of the pore water have been introduced at the macroscopic level. Other work-conjugate variables relevant for the constitutive modeling of double-porosity unsaturated media have also been identified, consisting of the modified suction as conjugate of the increment of the macrostructural degree of saturation and the microstructural effective stress as conjugate of the microstructural volumetric strain increment. A hydromechanical model for unsaturated expansive clays taking into account the interaction between the micro- and the macrostructures in expansive clays can thus be built. Based on the bounding surface concept, an anisotropic loading – collapse yield surface has been introduced to reproduce the three-dimensional mechanical behavior. To analyze the model capabilities, two series of laboratory tests consisting of multiple wetting and drying cycle tests on Boom clay and triaxial tests on Zaoyang (ZY) expansive clay were simulated. The comparisons between numerical and experimental results show that the model can reproduce with reasonable accuracy the mechanical behavior and the water retention characteristic of unsaturated expansive clays.

scholarly journals Statistical Law and Predictive Analysis of Compressive Strength of Cemented Sand and Gravel

2020 ◽  
Vol 27 (1) ◽  
pp. 291-298
Author(s):  
Shoukai Chen ◽  
Yongqiwen Fu ◽  
Lei Guo ◽  
Shifeng Yang ◽  
Yajing Bie
Keyword(s):  
Compressive Strength ◽  
Back Propagation ◽  
Back Propagation Neural Network ◽  
Predictive Analysis ◽  
Distribution Law ◽  
Data Set ◽  
Cemented Sand ◽  
Mix Proportion ◽  
Kolmogorov Smirnov ◽  
Sand And Gravel

AbstractA data set of cemented sand and gravel (CSG) mix proportion and 28-day compressive strength was established, with outliers determined and removed based on the Boxplot. Then, the distribution law of compressive strength of CSG was analyzed using the skewness kurtosis and single-sample Kolmogorov-Smirnov tests. And with the help of Python software, a model based on Back Propagation neural network was built to predict the compressive strength of CSG according to its mix proportion. The results showed that the compressive strength follows the normal distribution law, the expected value and variance were 5.471 MPa and 3.962 MPa respectively, and the average relative error was 7.16%, indicating the predictability of compressive strength of CSG and its correlation with the mix proportion.

Influence of drainage and root biomass on soil mechanical behavior in triaxial tests

2021 ◽  
Author(s):  
Mehtab Alam ◽  
Yuan-Jun Jiang ◽  
Muhammad Umar ◽  
Li-jun Su ◽  
Mahfuzur Rahman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Root Biomass ◽  
Triaxial Tests

Micro Parameters Sensitivity of Coarse Grained Material in Mechanics and Deformation Based on PFC3D

2016 ◽  
Vol 873 ◽  
pp. 115-119
Author(s):  
Zhi Hua Zhang ◽  
Xie Dong Zhang ◽  
Hong Sheng Qiu ◽  
Bei Yang Zhang
Keyword(s):  
Weighted Average ◽  
Shear Stiffness ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Analysis Method ◽  
Particle Rotation ◽  
Sensitivity Curves ◽  
Coarse Grained Material ◽  
Strength And Deformation

In order to study the effects of various parameters on macro-mechanical and deformational characteristics of coarse grained material based on discrete element method, triaxial tests have been conducted. Weighted average assembling method is used to assemble the numerical model based on PFC3D. The ratio of normal and shear stiffness of particles (kn/ks), shearing rate and friction coefficient are chosen as micro parameters to analyze the influential sensitivity. Curves of stress-strain intensity are taken as the mechanical analytic method. The particle rotation field as deformation analysis method is proposed to sort the sensitivity of these parameters in strength and deformation of coarse grained material. The research shows that the parameters have a certain effect on the strength and deformation of coarse grained material. kn/ks has the greatest influence on both. The sensitive list of the strength and deformation hopefully can be discussed with the relevant scholars, which can provide a reference for the adjustment of micro parameters in numerical field.

scholarly journals GEOLOGICAL ASSISTED ON WATER RESOURCES PLANNING IN MOUNTAINOUS CATCHMENTS IN KUNDASANG, SABAH, MALAYSIA

2020 ◽  
Vol 4 (1) ◽  
pp. 26-31
Author(s):  
Rodeano Roslee
Keyword(s):  
Water Resources ◽  
Geological Mapping ◽  
Coarse Grained ◽  
Water Resources Planning ◽  
Groundwater Levels ◽  
Deep Aquifers ◽  
Short Period ◽  
Catchment Areas ◽  
Sand And Gravel ◽  
Resources Planning

Based on geological mapping and geohydrologic data, water resources planning in mountainous catchment areas in Kundasang are outlined. The area is underlain by thick Paleogene clastic sediment and old Quaternary gravels. These rock units are carved by numerous lineaments with complex structural styles developed during series of regional Tertiary tectonic activities. The tectonic complexities reduced the physical and mechanical properties of the rock units and produced intensive displacements and discontinuities among the strata, resulting in high degree of weathering process and instability. The weathered materials are unstable and may cause subsidence and sliding induced by high pore pressure subjected by both shallow and deep hydrodynamic processes. Evaluation of 60 boreholes data in the study area reveals that the depth of the groundwater table ranges from 1.90 m (6 feet) to 11.20 m (35 feet) deep. The groundwater level in the study area fluctuates even within a short period of any instability of climatic change. The Quaternary sand and gravel layers with variable thickness defined the major shallow aquifers within the underlying weathered materials while the highly fractured sedimentary rocks defined the major deep aquifers. Most of the aquifers within the top unconsolidated weathered clastic material are under unconfined condition. The sedimentary formations are coarse-grained clastic materials generally contain fractured porosity and exhibit higher permeability. However, below subsurface, much of the groundwater is partially confined. Movements of groundwater are sufficiently restricted area to cause slightly different in head depth zones during periods of heavy pumping. During periods of less draught, the various groundwater levels will be recovered to their respective original level. This condition resulted from discontinuous nature of sediments where zones of permeable sand and gravel are layered between less permeable beds of silt and clay. Aquifer characterization and geological data are given to assist the local agencies on the water resources planning of the study area.

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